1. Field of the Invention
This invention relates to a pearlescent concentrate in the form of a free-flowing, aqueous dispersion free from ionic surfactants.
2. Statement of the Related Art
Aqueous preparations of surfactants and cosmetic preparations may be given a pearlescent, aesthetically pleasing appearance, by incorporation of substances which, after cooling, precipitate in the form of fine crystals resembling mother-of-pearl in appearance and which remain dispersed in the preparations. Known pearlizers include, for example, the mono- and diesters of ethylene glycol, propylene glycol and oligomeric alkylene glycols of this type or glycerol with C.sub.16-22 fatty acids and also monoalkanolamides of C.sub.12-22 fatty acids with C.sub.2 or C.sub.3 alkanolamines.
It is also known that the pearlizers mentioned form stable dispersions in water or in aqueous surfactant solutions and that the concentrated pearlescent dispersions obtained in this way may be added without heating to the preparations to be pearlized, so that there is no need for the heating and cooling otherwise necessary for incorporation to form the pearlescent crystals.
Pearlescent concentrations based on the pearlizers mentioned above are disclosed, for example, in British Pat. No. 1,230,413 (and corresponding published German patent application No. 16 69 152) as well as in published Japanese patent application No. 56-71,021 (and corresponding Chemical Abstract 95: 156,360). The pearlescent concentrates disclosed in the Japanese reference have the disadvantage that they are not free-flowing and do not form stable, free-flowing dispersions upon dilution with water. This makes the concentrates extremely difficult to handle and process on an industrial scale. The pearlescent concentrates known from British Pat. No. 1,230,413 contain anionic surfactants for stabilizing the dispersion in the liquid state. However, the presence of ionic surfactants is undesirable in numerous applications of pearlescent concentrates of the type in question because imcompatibilities with formulation constituents of opposite ionicity can arise with adverse effects upon the stability of the dispersions.
Accordingly, it is very desirable to provide pearlescent concentrates which are free-flowing at ambient temperatures, (approximately 10.degree. to 30.degree. C.), do not contain any ionic surfactants or dispersants and, nevertheless, remain stable in storage for several months without the pearlescent crystals sedimenting or rising to the surface.
In addition, the pearlescent concentrates should have a pearlescence which is stable to at least 50.degree. C. and which remains intact in the associated preparations despite variations in temperature. The pearlescent crystals should have a high luster and, even after melting or dissolution by heating beyond their melting point, should reassume the same lustrous, uniform crystal form on cooling.